"think it advisable to" is correct and usable in written English.
It is usually used to express a decision or opinion about something that is considered wise or suitable to do. Here is an example: "After considering the risks, I think it advisable to postpone the project until next quarter."
Like the wild raccoon that dawdled onto the stage during the excellent performance that night, we thought it advisable to let him wander off into the dark of Central Park.
But Gideon values speed over accuracy and even though he said he had checked his work, I thought it advisable to take a closer look at it.
These generations had sacrificed so much for the good of the country, and old-age poverty rates were so high, that policymakers thought it advisable to use the program to prevent these Americans from enduring deprivation in old age.
MALLOY: We suggest, Margaret and I — your sisters, too, think it advisable — that you go to some rest cure institution for a time and build up in body and mind.
The justification for the latter was that they "did not think it advisable for the company to adopt a policy limiting the ability of the board or the Management Development and Compensation Committee to make decisions about individual employment arrangements in the exercise of their business judgment".
One author suggests that, in such circumstances, the phrases "almost certainly present" or "almost certainly absent" may be useful if we think it advisable for the patient's sake to stop further imaging workup [3].
I don't know if you wd rather leave it to me to say I don't think it advisable she should see so much of you etc. or whether you wd rather do it in your own way ..
Even if elected or appointed officials can perform better than citizens, Mill thought it advisable for citizens to participate "as a means to their own mental education—a mode of strengthening their active faculties, exercising their judgment, and giving them a familiar knowledge of the subjects with which they are thus left to deal.
The statement said the Holy See thought it "advisable" for the bishop to spend an unspecified time away from Limburg.
